Air feed device for valve retract system in pneumatic acoustic source



March 25, 1969 M. o. JOHNSON 3,434,562

AIR FEED DEVICE FOR VALVE RETRACT SYSTEM IN PNEUMATIC ACOUSTIC SOURCE Filed Aug. 28, 1967 Sheet Of 3 FIG. y 2

RETRACT AIR TUBE 4of- I CHAMBER f I 4 l .sg

INVENTOR MALCOLM O. JOHNSON @maw ATTORNEY March 25, 1969 M. o. JOHNSON AIR FEED DEVICE FOR VALVE RETRACT SYSTEM IN PNEUMATIC ACOUSTIC SOURCE Filed Aug. 28. 1967 Sheet FIG.

AIR SUPPLY INVENTOR MALCOLM o. JOHNSON M@ t W ATTORNEY March 25, 1969 M. o. JOHNSON 3,434,562

AIE FEED DEVICE FOR VALVE RETRACT SYSTEM VIN PNEUMATIC ACOUSTIC SOURCE 3 Filed Aug. 28. 1967 Sheet of 3 FIG. 4

NVENTOR MALCOLM O. JOHNSON Magd-1 ATTORNEY United States Patent O N' AIR FEED DEVICE FOR VALVE RETRACT SYSTEM IN PNEUMATIC ACOUSTIC SOURCE Malcolm O. Johnson, Dallas, Tex., assignor to Mobil Oil Corporation, a corporation of New York Filed Aug. 28, 1967, Ser. No. 663,677 Int. Cl. GlOk 11/00 U.S. Cl. 181-.5 1 Claim ABSTRACT OF THE DISCLOSURE The specification discloses a repetitive marine acoustic source formed by a rigid chamber for confining high pressure gases and having a controllable spool-shaped valve -for rapidly releasing the high pressure gases into the water to generate an acoustic pulse. The valve has an aperture extending axially therethrough in which is secured a retract piston slidably mounted within a retract chamber. Gas is fed to the retract chamber through the top of the source by way of a flexible conduit and an aperture extending through the retract piston for retracting the spool-shaped valve to its closed position following the generation of an acoustic pulse.

Background ofthe invention This invention relates to a novel arrangement for feeding air to a retract chamber in a pneumatic acoustic source employed for generating acoustic pulses repetitively in water for marine seismic operations.

In -a United States copending patent application by Bernard Otto, Repetitive Pneumatic Acoustic Source for Marine Seismic Surveying, Ser. No. 666,676, iiled Aug. 28, 1967, and assigned to the same assignee as the present invention, there is disclosed a pneumatic acoustic source which comprises a rigid chamber having lan outlet port which is opened and closed by a fast-acting, spool-shaped valve. In operation, the valve is moved to close the port and the chamber is pressurized with high gas pressure. The valve then is actuated rapidly to open the port to allow the pressurized gas to be released rapidly into the water to generate an acoustic pulse. The cycle is repeated periodically to generate repetitive `acoustic pulses in water.

In the source developed, the valve has an aperture extending axially therethrough and which is opened to the water. A valve retract mechanism is located within the aperture and which comprises a pressure chamber, iixed rigidly with respect to the main chamber, and a retract piston. 'Ihe retract piston is iixed to the spoolshaped valve and supported to slide within the retract chamber. Pressurized air is injected into the retract chamber to move the retract piston and hence the quick-acting valve to its closed position following the generation of an acoustic pulse.

The acoustic source developed is a large source having a volume of about nine cubic feet. Its chamber was designated to withstand gas pressures up to about 500 p.s.i. Upon release of such high pressure gases into the water, forces of great magnitude were produced which had a detrimental effect on some of the periphery equipment or mechanisms of the source. One mechanism which was Iaffected was the conduit which supplied air to the retract chamber. Initially it was coupled to the rigid structure forming the retract chamber and led thereto from the bottom of the source adjacent the outlet port. The large forces developed, however, severely damaged this conduit and its coupling members after a period of time making frequent repairs necessary.

`In accordance with the present invention, the problem was solved by feeding air to the retract chamber 3,434,562 Patented Mar. 25, 1969 through the movable retract piston which is located away from the outlet port. The retract piston has a long stem extending therefrom and which is coupled to the top portion of the spool-shaped valve. In the present system, this stem has an aperture extending axially therethrough and leading to the retract chamber. A flexible conduit is coupled to the top end of the stem whereby pressurized air may be supplied to the retract chamber by way of the ilexible conduit and the aperture extending through the stem ofthe retract piston.

Brief description of the drawings FIGURE 1 illustrates the acoustic source, to which the present invention is directed, in the environment in which it is to be used;

FIGURE 2 is a cross-sectional view of the acoustic source and its quick-acting valve;

FIGURE 3 is a cross-sectional View of the acoustic source showing a side view of the quick-acting valve in the pressure chamber and a schematic illustration of the equipment and instrumentation employed for operating the source;

FIGURE 4 is an enlarged cross-sectional view of the source showing the air feed device for the valve retract system as initially developed; and

lFIGURE 5 illustrates a iitting used to couple the llexible air feed hose to the stem of the movable valve retract piston as provided in the present invention.

Operation of acoustic source Referring now to FIGURE 1, the acoustic source to which the present invention is directed is shown supported in water from a boat 31 by a cable arrangement 32 and supporting arms 33. As can be seen from the crosssectional View of FIGURE 2, the acoustic source comprises enclosing wall structure 34 forming a pressure chamber 35 and which has an outlet port at the lower end to be coupled to water. The outlet port comprises aperture 36 formed at the lower end of enclosing structures 34 and a plurality of laterally extending slots 37 extending through cylinder 38. A quick-opening, spool-shaped valve 40 is provided for opening and closing the outlet port. When the valve is in a closed position, the chamber is pressurized with high gas pressure. At a desired time, the valve 40 is actuated for sudden downward movement to allow the high gas pressure to escape rapidly into the water by way of the outlet port to generate an acoustic pulse.

As illustrated in FIGURES 2 and 3, the valve 40 comprises a lower release piston or rim 41, interconnecting tubular member 42 and an upper `or valve control rim 43. Tubular member 42 has an upper extension 44 and an aperture 45 extending axially therethrough. The valve 40 is supported for axial movement from a closed position as shown in FIGURES 2 and 3 to a downward open position whereby lower rim 41 is positioned near the lower end of cylinder 38. When the Valve 40 is moved to a closed position, the outlet port is sealed by lower piston ring seals 46 coupled to lower rim 41. In this position, the chamber 35 is pressurized by an arrangement including an air supply 50, located on the boat, solenoid controlled valve 51, exible conduit 52a leading to the source, rigid conduit 52h, check valve 53, and main air inlet 54.

In addition, in the valves closed position, a controlannulus 60 is formed between the top surface of control rim 43 and the upper chamber structure 61 of the source. Upper seal 62, coupled to chamber structure 61, contacts the upper surface of control rim 43 to seal the annulus from the high gas pressure in the main chamber 35. Annulus 60 normally is maintained at a low pressure when the valve 40 is closed by an arrangement including normally closed solenoid valves 64 and shuttle valves 65, the latter of which vent annulus 60 to the water by way of passageways 66, valves 65, and vents 67. The area of the control rim 43 within the upper seal 62 is greater than the area of the release rim 41 within the lower seal 46. Thus, a net upward force is applied to the quick-opening valve maintaining it in a closed position as the chamber is pressurized.

The fast-acting valve is actuated to release the pressurized gas from the chamber by increasing the pressure in control annulus 60. This is done by simultaneously opening solenoid valves 64, of a dual triggering system, to allow air to flow from conduit 52b to valves 65 by way of conduits 68, valves 64, check valves 69, and passageways 70. The air causes shuttle valves 65 to close the vents 67 for ow to annulus 60 through passageways 66. The increase in pressure in annulus 60 causes valve 40 to move downward to a position whereby the top surface of the control rim 43 disengages the upper seal 62. When this occurs, the high gas pressure in the chamber 35 acts upon the top surface of the control rim 43 to upset the balance of force and rapidly move the quick-acting valve 40 downwardly to allow the high gas pressure in the chamber 35 to be released immediately into the water by way of aperture 36 and slots 37 to generate an acoustic pulse.

The mechanism for retracting the valve 40 to its closed position following the generation of an acoustic source comprises an air retract chamber 80 formed by cylinder 81 and a retract piston 82, both of which are supported within the central aperture extending through the tubular interconnecting member 42 of the valve 40. Cylinder 81 is supported rigidly with respect to the chamber Wall structure 34 by way of tubular support member 83, hub 84, and cylinder 38. Piston 82 slides within chamber 80 and is coupled rigidly to the valve 40 for movement therewith. Piston 82 is coupled to the valve 40 by way of stem 85, rim 86, radial spokes 87, and rim 88. Pressurized air is injected continuously into chamber 80 for valve retract purposes. Following the generation of an acoustic pulse and after the high gas pressure is released from the pressure chamber 35, the air within t-he retract chamber acts over the entire surface 90 of the retract piston 82 and moves the piston 82 and hence the quick-acting valve 40 to its closed position.

Detailed description of the invention Air is fed from air supply to source 30, for retract purposes, by a exible conduit 91. This conduit extends to manifold 92 which is coupled rigidly to chamber structure 34, near the top of the source 30 and close to the top of stem 85, by means indicated by dashed line 93. Air is injected into air chamber 80 from manifold 92, by way of a flexible conduit 94, and aperture 95 extending through stem 85. This arrangement is unique in that it supplies air to the c-hamber 80 by way of the movable member (piston 82 and stem 85) rather than through the xed wall structure forming the chamber 80. It has advantages in that it avoids the effect of the high pressure forces produced adjacent the outlet port which heretofore had affected the conduit employed for supplying pressurized air to the chamber 80.

For example, referring to FIGURE 4, the earlier arrangement for supplying air to the chamber 80 included a rigid tubular member 100, extending to the chamber 80 through the bottom of the source 30 and adjacent the outlet port thereof. The upper end of the conduit 100 was threaded into aperture 101 extending through the lower Wall structure 102 forming the chamber 80. The lower end of conduit 100 was secured to conduit 103 by coupling members 104 and 105. Conduit 103 was a rigid member secured to rim portion 84a of hub 84 (by means not shown) and extended upward along the outside of cylinder 38 to conduit 91 for feeding air to chamber 80 by way of conduit 103, coupling members 104-105, and conduit 100. Repeated use of the source caused severe damage or destruction and hence loss of members 103, 105, 104, and 100.

As mentioned above, the problem was solved by feeding air into chamber through the top of the source by way of flexible conduit 94 and aperture 95 extending through the movable stem of retract piston 82. Valve 40 and hence stem 85 travel about eight inches in the opening movement of the valve. Conduit 94 is a reinforced rubber hose. It has a length of 3l inches which is sufficient to allow it to follow the valve 40 during movement thereof without affecting the connection of the conduit 94 to the stem 85 or to the manifold 92.

Air hose 94 has its ends coupled to stem 85 and to manifold 92, respectively, by ttings, one of which is illustrated in FIGURE 5. Each tting comprises a metallic tubular member having a threaded end 96, a bolt-shaped central portion 97, and a barbed end 98. End 97 is threaded into stem 85 or manifold 92 while end 98 is inserted into one end of air hose 94 and clamped thereto by clamp 99.

Referring again to FIGURE 2, there will be described details of the quick-acting valve structure, the valve retract mechanism, and a valve deceleration system. These features also are disclosed and claimed in the aforementioned copending application. The arrangement for supporting the quick-acting valve centrally of the exterior wall structure 34 and for movement axially thereof comprises a lower wear ring coupled to the lower rim 41 and an upper bearing member 111 coupled to the upper chamber structure. Wear ring 110 slides on the inner surface of slotted cylinder 38 which is made up of an inner slotted liner 112 and an outer slotted cylinder 113. the latter of which is coupled to the chamber structure `34 by way of bolts 114. Hub 84 is coupled to cylinder 38 by way of bolts 115. Member 83 is secured to hub 84 by cap 116 threaded to member 83 at 116a after member 83 passes through hub 84. Tubular member 81 is threaded onto member 83 at 117. Radial spokes 87 and inner and outer rims 86 and 88, respectively, are machined from a solid piece of metal. Rim 88 is threaded to tubular extension 44. Inner rim 86 is coupled to stem 85 by threaded cap 118 and support 119.

Central member 83 has two keys 120 secured thereto by bolts 121 which cooperate with slots (not shown) formed in the interior surface of valve 40 for preventing rotation of the valve during its upward and downward movement. Tubular member 81 has a slotted end cap 122 threaded thereto and through which the stem 85 slides. The exterior diameters of tubular member 81 and slotted end cap 122 are smaller than the interior diameter of the aperture 45 extending through the quick-acting Valve 40 thereby providing a central region exposed to and containing water when the source is immersed in Water. Water may pass into and out of this region by way of the aperture 45 and by way of water slots 123 formed on the outer periphery of central support member 83. These water slots extend from the top portion of member 83 to apertures 124, the latter of which allow water to pass interiorly of member 83 intermediate its ends. Thus, the central Water region extends completely through the quick-acting valve 40.

The arrangement for decelerating the valve comprises a lower water trap region or chamber for decelerating the quick-acting valve 40 at the end of its opening movement and an upper or return water trap chamber 131 for decelerating the quick-acting valve 40 at the end of its return movement.

Lower water trap region 130 is formed as the lower rim portion 132. slides around the enlarged cylindrical portion 133 of central support 83. Water trapped in this region decelerates the valve 40. Water escapes downward through the small clearance between the exterior surface of member 133 and the interior surface of member 132. The, exterior surface of member 133 is tapered toward its upper end to provide a variable orifice to obtain uniform deceleration of the valve. Upon movement of the valve 40 downward, water below the lower rim 41 passes outward and downward by Way of slots 37 and apertures 134 formed in connecting hub 84.

As the quick-acting valve and hence the retract piston 82 moves downwardly, water from the annular water region within the quick-acting valve 40 liows through laterally extending apertures 135, formed in end cap 122, into the chamber region 131. Upon upward movement of the valve 40 and the retract piston 82, water trapped within this chamber decelerates the valve at the end of its return movement. It escapes through apertures 135 by way of the small clearance between the exterior surface of retract piston 82 and the interior surface of end cap 122. The exterior surface of retract piston 82 is tapered toward its upper end to provide a variable orifice to obtain uniform deceleration of the valve.

In the preferred embodiment, the upper seal 62 comprises an elastomer O-ring and a metal seal ring located within a slot formed in the ychamber structure 61. The elastomer seal ring is located between the walls of the slot and the metal seal ring, the latter of -which has a narrow end extending from the slot and which contacts the upper surface of the control rim 43 to form the control annulus 60. In addition, pressurized gas is applied to the slot to form an elfective seal. This gas is obtained from the pressure chamber 35 and applied to the sealing slot by Way of a labyrinth extending through the structure 61. This seal arrangement is disclosed and claimed in copending application iiled Aug. 28, 1967 by Ellis M. Brown et al., Seal for Pneumatic Source, Ser. No. 663,664, and assigned to the same assignee as the present invention.

In one embodiment, pressurized air only may be employed to pressurize the chamber 35. In this embodiment, the solenoid controlled valve 51 is operated during each cycle by a control mechanism (not shown) to allow air to iiow into chamber 35. After the chamber 35 is lled, the same control mechanism (which may be cam operated system or an electronic switching system) operates solenoid controlled valve 64 to actuate the valve 40 to release the pressurized air into the water as described previously. The source 30 may be operated to produce acoustic pulses at a repetition rate of once every six seconds.

In an-other embodiment, diesel fuel may be injected into the chamber 35 from a plurality of fuel injectors 140 to form a combustible mixture with the pressurized air injected. This combustible mixture is ignited by a plurality of igniters 141. In the arrangement shown, the diesel fuel injectors and igniters are located alternately in two spaced planes and positioned whereby the diesel fuel injectors in the upper planes spray fuel toward the igniters in the lower planes and the injectors in the lower plane spray Ifuel toward the igniters in the upper plane. In addition, each igniter has a shield 142 located on one side thereof to prevent cooling thereof by the air injected from inlet 54. This air s injected in a swirling path around the chamber to enhance the formation of a good combustible mixture. This arrangement also is disclosed and claimed in copending application filed Aug. 28, 1967, by George B. Loper having the title Fuel Mixing and Ignition System in Pneumatic Acoustic Source, Ser. No. 663,663, and assigned to the same assignee as the present invention.

The shuttle valves 65 lalso are disclosed and claimed in the aforementioned application to Bernard Otto and comprise movable valves which normally are biased to vent the annulus 60 by way of passageways 66 and vents 77. Actuation of valves 64 allows the air to ow to the shuttle valves which air moves the shuttle valves to a position to close the vent but allows the air to pass from passageways to 66 for triggering the quick-acting valve 40.

What is claimed is:

1. An acoustic source for generating acoustic pulses in water for exploratory purposes comprising:

a high pressure chamber having a iirst end and outlet port means spaced from said first end to be coupled to water,

movable valve means including a release member supported for movement in a first direction away from said first end to an open position for opening said port means and in an opposite direction toward said first end to a closed position for closing said outlet port means,

means for introducing a Huid into said chamber when said valve means is in a closed position to form a high gas pressure in said chamber,

means for actuating said valve means to move said valve means rapidly to an open position to open said outlet port means to `allow said pressurized gas in said chamber to be released rapidly into the water to generate an acoustic pulse,

said valve means including structure movable concurrently therewith and forming a retract chamber,

said movable valve means having an aperture extending therethrough,

1 said retract chamber being located within said aperture and comprising cylindrical wall structure and a lower closed end,

said movable structure comprising a retract piston supported for movement within said cylindrical wall structure,

a stem extending from said retract piston in a direction away from said release member and said outlet port means,

means for rigidly securing said stem to said valve means for movement therewith,

said stem and said retract piston having an aperture extending therethrough and leading to said retract chamber,

conduit means extending from a source of pressurized gas to adjacent said acoustic source, and

a exible conduit being coupled from said conduit means to said stem for supplying pressurized gas to said retract chamber by way of said aperture extending -through said stern and retract piston for moving said valve means to its closed position following the generation of an acoustic pulse,

said flexible conduit having a length sufficient to follow said valve and said stem during movement thereof without affecting the connection of said flexible conduit to said stem and to said conduit means.

References Cited UNITED STATES PATENTS BENJAMIN A. BORCHELT, Primary Examiner. G. H. GLANZMAN, Assistant Examiner. 

